Implantable neurostimulation devices have been used in the past 10 years to treat acute or chronic neurological conditions. Deep brain stimulation (DBS), the mild electrical stimulation of sub-cortical structures, belongs to this category of implantable devices, and has been shown to be therapeutically effective for Parkinson's disease, dystonia, and tremor. New applications of DBS in the domain of psychiatric disorders (e. g. obsessive compulsive disorder, depression) are being researched and show promising results. In existing systems, the leads are connected to an implantable current pulse generator.
Currently, lead systems are under development with more, smaller electrodes in a technology based on thin film manufacturing. These leads will have multiple electrode areas and will enhance the precision to address the appropriate target in the brain and relax the specification of positioning. Meanwhile, undesired side effects due to undesired stimulation of neighbouring areas can be minimized.
Probes that are based on thin film manufacturing are disclosed, e.g., by US 2008/0255439 A1, and have been used in research products in animal studies.
These novel systems consist of a lead made from a thin film based on thin technology. The thin films are assembled on a core material with a cylindrical shape to form a lead. Such a probe is disclosed by US 2007/0123765 A1, which is showing a modular multichannel microelectrode array and methods of making the same.
As the thin film wires and traces for the lead are relatively thin and long in these leads, the electrical resistance gives rise to substantial differences between the driving voltage at the current source and the driving voltage at the distal end. The current pulse can be well controlled though, and as such, the potential at the distal-end is kept within safe limits. However, there is no active voltage control of the potential at the distal end of the lead. For therapeutic applications that require potential control at the distal end, active voltage monitoring at the distal end is required. For safety reasons, voltage monitoring can be beneficial too. Sensing near the electrode can be also beneficial to create an active feedback loop to compensate for pulse to pulse variation between various drivers in the electronic circuit.
It is therefore an object of the present invention to provide a lead for brain applications and a deep brain stimulation system having improved properties, in particular that a voltage monitoring at the distal end of a probe of a brain stimulation system can be conducted.
Accordingly, a lead for brain applications comprises at least one distal section and at least one electrode, whereby the at least one electrode is arranged in the distal section and whereby the at least one electrode is connected directly and/or indirectly with at least one first connecting trace and at least one second connecting trace.
The at least one electrode may be connected directly and/or indirectly in close vicinity of the electrode area with at least one first connecting trace and at least one second connecting trace.
The lead may be a component of a Deep Brain Stimulation probe. The electrodes can be connected to electronic means to provide the pulses and measure signals at the proximal end of such a DBS probe, whereby the electronic means are arranged outside of the brain. Alternatively, the electronic means can be integrated into the probe, in close vicinity of the distal end of the probe and thus the electronic means are arranged inside of the brain.
Thereby, the advantage may be achieved that one connecting trace can be used for, e.g., power supply, and one connecting trace can be used for, e.g., voltage monitoring. The lead for brain applications can be a lead having a thin film based probe design. The brain applications can be, e.g., deep brain stimulation (DBS). Thus, especially the further advantage may be achieved that, e.g., voltage monitoring at the distal end at the location of the stimulation electrode is enabled.
Additionally, it is possible that the first connecting trace is configured such that electrical power can be supplied to the electrode.
Preferably, it is possible that the second connecting trace is configured such that a voltage monitoring of the electrode can be conducted.
In a further preferable embodiment it is possible that the first connecting trace and the second connecting trace are directly connected to the electrode, whereby preferably the first connecting trace and the second connecting trace are directly connected from the proximal end of the lead to the electrode.
Further preferably, it is possible that the first connecting trace is directly connected to the electrode and the second connecting trace is indirectly connected to the electrode.
Especially, the second connecting trace may be connected to the first connecting trace at a connecting point, which is arranged adjacent to the electrode. In particular, the second connecting trace does not necessarily need a connection to the electrode area itself. A design with connection in proximity of the electrode can be used also, which is, e.g., preferred when several electrodes are to be arranged with high density.
The lead may comprise a plurality of electrodes. E.g., several electrodes or all electrodes can be configured such that the electrodes are capable of providing electrical stimulation to the tissue and each of the electrodes is capable of detecting electrical signals. Thereby, the advantage is achieved that a tailor-made stimulation can be conducted by the probe which is equipped with a plurality of electrodes and that thereby the brain tissue to be stimulated can be stimulated with high accuracy. Additionally, the advantage is achieved that also electrical signals can be determined and that this determination process can be done with high accuracy. The electrodes may be arranged in a predetermined geometrical manner forming an array on the probe and that the probe may be implanted at a certain position in a target area of the brain. Due to the fact that the electrodes are arranged in a predetermined geometrical manner a correlation of signals received from the target region and the arrangement of the electrodes can be generated and the necessary electrodes for an optimal neurostimulation treatment can be selected. Advantageously, the target area may then be stimulated with high accuracy, since the array electrodes allows a precise and specific stimulation of the target area.
Preferably, it is possible that the lead is a lead with a thin film and/or whereby the first connecting trace and the second connecting trace are a thin film structure and/or are a part of a thin film structure. Common thin film technologies may be used to manufacture the thin film for the lead, e.g., chemical deposition methods like plating, chemical vapour deposition (CVD), or chemical solution deposition (CSD), etc., physical deposition methods like sputtering, pulsed laser deposition, cathodic arc deposition, or electrohydrodynamic deposition, etc., or other deposition methods like molecular beam epitaxy (MBE) or topotaxy, etc. These methods may be used, in combination with thin film structuring methods, such as photolithography and etching.
Further preferably, the thin film structure may comprise and/or may be connectable to at least one controlling means, whereby the controlling means is configured such that a voltage monitoring can be conducted in connection with the second connecting trace.
Additionally, it is possible that the first connecting traces are arranged in a separate first level and that the second connecting traces are arranged in a separate second level of the thin film structure. It is possible that the traces are embedded in a biocompatible polymer, which can include, e.g., parylene.
In a further preferred embodiment it is possible that the level of the first connecting traces has a first thickness and that the level of the second connecting traces has a second thickness, whereby the thickness of the level of the first connecting traces is thicker than the thickness of level of the second connecting traces. In particular, it is not necessary that the traces have to be manufactured next to each other. The second connecting traces can be manufactured in a separate metal layer or a separate layer level. The metal in the level that is used for the voltage sensing traces can be chosen relatively thin, because the resistivity of the track can be relatively high, especially due to the fact that the second connecting traces may be used for the voltage monitoring only. Voltage monitoring will not be compromised by high resistance in the track as it can be performed with high impedance measuring systems.
Preferably, in a possible embodiment of the deep brain stimulation system the deep brain stimulation system comprises at least one controlling means and/or is connectable to at least one controlling means, whereby the controlling means is configured such that a voltage monitoring can be conducted in connection with the second connecting trace. Advantageously, voltage monitoring can be used to enhance the safety of a DBS system.
It is furthermore possible that the controlling means is configured such that the current, especially the electrical power supplied by the first connecting trace, can be switched off or limited when a safety compliance limit is reached.
Additionally, it is possible that the controlling means is configured such that the voltage applied to the at least one electrode can be determined and controlled and/or that the controlling means is configured such that resistance differences in the first connecting traces and/or resistance differences in the second connecting traces can be electronically corrected. Also, differences in the electronic means, respectively the electronic unit, can be corrected, for example.
Further preferably, it is possible that the controlling means is configured such that changes of the at least one electrode in the brain after implantation can be measured and that the driving of the electrode can be adjusted accordingly.